1. Field of the Invention
The present invention relates broadly to the art of making glass and, mmore particularly, to an improved method and apparatus for supplying glass making materials to a tank furnace wherein the melting rate of the materials is substantially increased.
2. Description of the Prior Art
In melting glass making materials in conventional continuous tank-type furnaces, considerable difficulty has been encountered in obtaining uniform melting of the materials and utilizing the maximum efficiency of the heat supplied because of the normal practice of supplying heat from overhead flames to melt the raw materials and refine the melted materials at elevated temperatures. Accordingly, many methods and devices have been proposed for feeding glass making materials into continuous glass melting furnaces in efforts to secure uniform melting of the materials in an efficient manner and minimum period of time.
Among the types of feeding devices employed in the past are those which deposit glass making materials in localized lumps or piles at various locations adjacent the entrance end of the melting tank. The material, as it is melted, flows toward the exit end of the tank because of the thermal currents naturally occurring in the tank and the withdrawing of glass from its exit end. In other types, a layer of glass making materials is continuously deposited on the molten glass in the so-called doghouse adjacent the entrance end of the tank and mechanically pushed into the melting tank to form a blanket of material on top of the molten glass in the tank. It has been observed that when glass making materials are dropped by gravity so as to fall freely onto the surface of the molten glass bath, air is entrapped in the materials and acts as an insulating medium, preventing heat from reaching the interior of the piles or blanket of unmelted glass making materials. Thus, higher temperatures are required to melt the materials in a given time, or if normal melting temperatures are employed, the time for melting the materials is substantially increased.
Tests have shown that compacted glass making materials have a faster heat-up rate than uncompacted glass making materials and thus, will reach their melting point in a shorter period of time than the time required for the uncompacted glass making materials to reach the melting point. Efforts have been made in the past to compact or densify the glass making materials before delivering them to the melting furnace. For example, in U.S. Pat. No. 3,325,298, various methods are disclosed for densifying batches of glass making materials in the mixing devices before they are delivered to the melting furnace. However, special handling may be required to maintain this densification as the glass making materials are removed from the mixer and deposited through the feeder into the forward end of the melting furnace.